add highlighting definition for MarkDown syntax

ICSharpCode.AvalonEdit/Highlighting/Resources/MarkDown-Mode.xshd

@@ -0,0 +1,61 @@
+<?xml version="1.0"?>
+<SyntaxDefinition name="MarkDown" extensions=".md" xmlns="http://icsharpcode.net/sharpdevelop/syntaxdefinition/2008">
+	<Color name="Heading" foreground="Maroon" exampleText="# Title #" />
+	<Color name="Emphasis" fontStyle="italic" exampleText="*this* is important!" />
+	<Color name="StrongEmphasis" fontWeight="bold" exampleText="**this** is more important!" />
+	<Color name="Code" exampleText="this is `int.GetHashCode()`" />
+	<Color name="BlockQuote" foreground="DarkBlue" exampleText="&gt; This is a\r\n&gt; quote." />
+	<Color name="Link" foreground="Blue" exampleText="[text](http://example.com)" />
+	<Color name="Image" foreground="Green" exampleText="[text][http://example.com/test.png]" />
+	<Color name="LineBreak" background="LightGray" exampleText="end of line      \r\n2nd line   " />
+	
+	<RuleSet ignoreCase="true">
+		<Span color="Heading">
+			<Begin>^\#</Begin>
+		</Span>
+		<Span color="StrongEmphasis" multiline="true">
+			<Begin>\*\*</Begin>
+			<End>\*\*</End>
+		</Span>
+		<Span color="StrongEmphasis" multiline="true">
+			<Begin>__</Begin>
+			<End>__</End>
+		</Span>
+		<Span color="Emphasis" multiline="true">
+			<Begin>\*(?![ ])</Begin>
+			<End>\*</End>
+		</Span>
+		<Span color="Emphasis" multiline="true">
+			<Begin>_</Begin>
+			<End>_</End>
+		</Span>
+		<Span color="Code" ruleSet="C#/">
+			<Begin>`</Begin>
+			<End>`</End>
+		</Span>
+		<Span color="Code" ruleSet="C#/">
+			<Begin>^\t</Begin>
+			<End>^(?!\t)</End>
+		</Span>
+		<Span color="Code" ruleSet="C#/">
+			<Begin>^[ ]{4}</Begin>
+			<End>^(?![ ]{4})</End>
+		</Span>
+		<Span color="BlockQuote">
+			<Begin>^&gt;</Begin>
+			<End>^(?!&gt;)</End>
+		</Span>
+		<Rule color="Image">
+			\!\[.*\]\[.*\]
+		</Rule>
+		<Rule color="Link">
+			\[.*\]\(.*\)
+		</Rule>
+		<Rule color="Link">
+			\[.*\]\[.*\]
+		</Rule>
+		<Rule color="LineBreak">
+			[ ]{2}$
+		</Rule>
+	</RuleSet>
+</SyntaxDefinition>

ICSharpCode.AvalonEdit/Highlighting/Resources/Resources.cs

@@ -42,6 +42,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			                                 ".booproj;.build;.xfrm;.targets;.xaml;.xpt;" +
 			                                 ".xft;.map;.wsdl;.disco;.ps1xml;.nuspec").Split(';'),
 			                         "XML-Mode.xshd");
+			hlm.RegisterHighlighting("MarkDown", new[] { ".md" }, "MarkDown-Mode.xshd");
 		}
 	}
 }

ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj

@@ -448,4 +448,7 @@
   <ItemGroup>
     <EmbeddedResource Include="Highlighting\Resources\PowerShell.xshd" />
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Highlighting\Resources\MarkDown-Mode.xshd" />
+  </ItemGroup>
 </Project>